Metal lines used for electrical connection between elements in a semiconductor device are completed as an intended line pattern through a process including the steps of depositing aluminum mainly to form a metal layer, patterning a photoresist on the metal layer to form a photomask, and dry etching the metal layer in a region not protected by the photomask using an etching gas.
Currently, a process for dry etching the metal layer is performed using reactive gases of Cl series such as Cl2 or BCl3. However, in the case of the reactive gases of Cl series, a problem arises in that the metal line is corroded unless the photomask is removed immediately after the metal layer is etched. This is because the aluminum metal layer is changed into a compound in the form of AlClx through a reaction with Clx and the compound causes the corrosion by reacting with moisture in the air when the compound is exposed in the air.
Therefore, conventionally, the photomask is generally removed under a vacuum state immediately after the metal layer is etched, and vapor and oxygen plasma ashing process has been used at a high temperature of 250° C. in order to remove chlorine composition absorbed on an entire surface of a wafer when the photomask is removed.
However, the above-described process has a problem in that the removal of the photomask is easily not performed. In addition, due to a problem of manufacture equipments, there is a problem in that the corrosion of the metal line occurs in the case that a process wafer has to be drawn out to the air immediately after the metal layer is etched.
As a result, it is not easy to form the metal line having the intended line pattern, and line defects of the semiconductor device are induced, which are major causes of malfunction of the semiconductor device.
To overcome these problems, techniques for etching an interlayer insulation film, a hard mask, etc., using etching gases of non-Cl series such as CF4, CHF3, C3F8, C2H6, and SF6, are disclosed in U.S. Pat. Nos. 6,238,582 and 5,886,410.